• Magazine of korean Tunnelling and Underground Space Association
• /
• v.21 no.1
• /
• pp.101-112
• /
• 2019

This case study presented a simplified failure mechanism approach used as a preliminary deformation prediction for the Mexico City's metro system expansion. Because of the Mexico City's difficult subsoils, Line 12 project was considered one of the most challenging projects in Mexico. Mexico City's subsurface conditions can be described as a multilayered stratigraphy changing from soft high plastic clays to dense to very dense cemented sands. The Line 12 trajectory crossed all three main geotechnical Zones in Mexico City. Starting from to west of the City, Line 12 was projected to pass through very dense cemented sands corresponding to the Foothills zone changing to the Transition zone and finalizing in the Lake zone. Due to the change in the subsurface conditions, different constructions methods were implemented including the use of TBM (Tunnel Boring Machine), the NATM (New Austrian Tunneling Method), and cut-and-cover using braced Diaphragm walls for the underground section of the project. Preliminary crown and excavation front deformations were determined using a simplified failure mechanism prior to performing finite element modeling and analysis. Results showed corresponding deformations for the crown and the excavation front to be 3.5cm (1.4in) and 6cm (2.4in), respectively. Considering the complexity of Mexico City's difficult subsoil formation, construction method selection becomes a challenge to overcome. The use of a preliminary results in order to have a notion of possible deformations prior to advanced modeling and analysis could be beneficial and helpful to select possible construction procedures.

• Nuclear Engineering and Technology
• /
• v.53 no.7
• /
• pp.2151-2161
• /
• 2021

Nuclear data (ND) sensitivity and uncertainty (S/U) quantification in shielding applications is performed using deterministic and probabilistic approaches. In this paper the validation of the newly developed deterministic program package ASUSD (ADVANTG + SUSD3D) is presented. ASUSD was developed with the aim of automating the process of ND S/U while retaining the computational efficiency of the deterministic approach to ND S/U analysis. The paper includes a detailed description of each of the programs contained within ASUSD, the computational workflow and validation results. ASUSD was validated on two shielding benchmark experiments from the Shielding Integral Benchmark Archive and Database (SINBAD) - the fission relevant ASPIS Iron 88 experiment and the fusion relevant Frascati Neutron Generator (FNG) Helium Cooled Pebble Bed (HCPB) Test Blanket Module (TBM) mock-up experiment. The validation process was performed in two stages. Firstly, the Denovo discrete ordinates transport solver was validated as a standalone solver. Secondly, the ASUSD program package as a whole was validated as a ND S/U analysis tool. Both stages of the validation process yielded excellent results, with a maximum difference of 17% in final uncertainties due to ND between ASUSD and the stochastic ND S/U approach. Based on these results, ASUSD has proven to be a user friendly and computationally efficient tool for deterministic ND S/U analysis of shielding geometries.

• Geomechanics and Engineering
• /
• v.37 no.4
• /
• pp.323-339
• /
• 2024

If the pressure exerted on the face of a tunnel excavated by TBM exceeds a threshold, it leads to failure of the soil or rock masses ahead of the tunnel face, which results in heaving the ground surface. In the current research, the upper bound method of limit analysis was employed to calculate the blow-out pressure of tunnels excavated in rock masses obeying the Hoek-Brown nonlinear criterion. The results of the proposed method were compared with three-dimensional finite element models, as well as the available methods in the literature. The results show that when σ_ci, m_i, and GSI increase, the blow-out pressure increases as well. By doubling the tunnel diameter, the blow-out pressure reduces up to 54.6%. Also, by doubling the height of the tunnel cover and the surcharge pressure exerted on the ground surface above the tunnel, the blow-out pressure increased up to 74.9% and 5.4%, respectively. With 35% increase in the unit weight of the rock mass surrounding the tunnel, the blow-out pressure increases in the range of 14.8% to 19.6%. The results of the present study were provided in simple design graphs that can easily be used in practical applications in order to obtain the blow-out pressure.

• Korean Chemical Engineering Research
• /
• v.45 no.2
• /
• pp.143-148
• /
• 2007

In hydrogen production for fuel cell by reforming city-gas, sulfur compounds, odorant in city-gas, are detrimental to reforming catalyst and fuel cell electrodes. We prepared metal salt impregnated ${\beta}-zeolite(BEA)$ to remove sulfur compound in city-gas by adsorption. The sulfur breakthrough adsorption capacity was changed depending on the concentration and species of metal salt. $AgNO_3$ impregnated BEA showed the highest sulfur breakthrough capacity among adsorbents used in this experiment(41.1 mg/g). But metal salt impregnated BEA such as $Ni(NO_3)_2/BEA$, $Fe(NO_3_)_3/BEA$, $Co(NO_3)_2/BEA$ showed a certain amount of sulfur adsorption capacity comparable to $AgNO_3/BEA$. Adsorption temperature effect, desorption study, and x-ray photoelectron spectroscopy analysis revealed that the dominant interaction between metal impregnated adsorbent and sulfur compounds was not chemisorption but physisorption.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.5 no.4
• /
• pp.361-370
• /
• 2003

In this study, the performance of water tightness of water expansional sealing material and gasket was evaluated. The water tightness test was performed varying the type of inner pressure condition, for which the water expansional sealing material was inundated for 5 days to evaluate the ability of water tightness. In order to carry out this test, we made use of two types of water expansional sealing material; general type and combined type with non-expansional rubber. In the case of gasket, EPDM gasket and complex gasket sticked to the water expansional sealing material were applied. The performance of water tightness depended on the construction defect and the deformation of segment. The construction defect and segment deformation were generally expressed by gap and offset of the construction joint. The results, of tests showed that the performance of water tightness was largely influenced by the gap between segments. Management criteria of gap and offset were proposed.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.11 no.2
• /
• pp.35-41
• /
• 1993

The height differences in Mean Sea Level is an important factor in geodetic leveling net, because MSL is the reference datum for height. Geodesists and Oceanographers agree on the height differences in MSL in the east-west direction, but they disagree almost always on the north-south slope, each suspecting systematic errors in the leveling methods of the others. A promising method for determining this slope is comparison of MSL at the tidal station connected by geodetic leveling. The slopes of the sea surface along the coast of Korean Peninsular is estimated from conventional local MSL at the tidal station and bench mark height of first order leveling net in Korea. As a reference level surface, MSL at Inchon is chosen. The results indicate that sea level rises along coast of Korean Peninsular from south to north about 5.5 cm/latitude. In the east-west direction, sea level along East Sea coast stands about 5 cm higher than that along Yellow Sea coast. These are not invariable but provisional phenomena. It may become certain provided that the exact MSL is estimated.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.15 no.3
• /
• pp.175-186
• /
• 2013

Based on Model Code 2010, flexural and residual strength, flexural toughness of SFRC with design strength of 60 MPa are evaluated. For comparisons, SFRC with design strength 40 MPa was tested. Distribution of steel fibers in crack surface of specimens was evaluated by visual inspection. The used steel fibers were hooked fibers with aspect ratio of 64, 67 and 80. In all specimens, mix ratio of steel fibers was 0.5% Vol. In results, only SFRC with the highest aspect ratio satisfied requirements specified in Model Code 2010. The results demonstrated that the use of high aspect ratio will provide enough flexural toughness for high strength concrete. Also, it is found that low slump of high strength concrete can help to enhance isotropic fiber distribution.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.15 no.1
• /
• pp.1-11
• /
• 2013

Steel fiber-reinforced concrete (SFRC) is widely used for tunnel lining structure such as shot-crete in NATM tunnel and segment in TBM tunnel. In tunnel fire accidents, structural performance of a lining is very important because the lining is the structure that directly exposed to fire. In this study, the effects of high temperatures, mix ratios and types on failure pattern, DPT tensile strength and coefficient of variation were investigated through Double Punch Tests (DPT) of SFRC subjected to high temperatures. In the results, it is confirmed that the residual DPT tensile strength increases as for SFRC and this is more in SFRC with higher mix ratio. But, the equation for evaluation of DPT tensile strength does not involve the number of failure surfaces SFRC specimens subjected to high temperatures, therefore, it is required to investigate more fracture energy in DPT tests.

• Proceedings of the KSAR Conference
• /
• 2001.03a
• /
• pp.85-85
• /
• 2001

본 연구는 돼지 난자의 체외 수정시 sucrose 첨가가 돼지 난자의 다정자 침입율에 미치는 영향을 조사하기 위하여 실시하였다. 돼지 난포란은 0.1% PVA, 3.05 mM D-glucose, 0.91 mM sodium pyruvate, 0.57 mM cysteine, 0.5 $\mu\textrm{g}$/$m\ell$ FSH, 0.5 $\mu\textrm{g}$/$m\ell$ LH, 및 10 ng/$m\ell$ EGF가 첨가된 TCM199 배양액에서 42-44 시간 동안 배양하여 체외 성숙을 유도하였으며, 2 mM caffeine과 0.1% BSA가 첨가된 체외수정용 mTBM 배양액에 3% sucorse를 첨가하여 6시간동안 수정을 유도하였다. 수정된 난자의 다정자 침입율을 조사하기 위해 체외수정 후 12, 13 및 14 시간대에 각각 1% orcein으로 염색하여 전핵 형성율을 조사하였다. 돼지 난자의 체외수정시 3% sucorse를 첨가하였을 때, 전핵 형성율을 조사한 결과 대조구에서 미수정, 1, 2, 및 3 PN 이상의 전핵 형성율은 각각 57.6 7.6, 9.7, 및 25%로, 처리구 74.2, 7.6, 13.6, 및 4.5% 에 비교하여 다정자 침입율이 유의하게 높았다(p<0.05). 그리고 3% sucorse를 첨가한 체외수정용 배양액에서 수정을 유도한 후 12, 13, 및 14 시간대별로 나누어 전핵 형성율을 조사한 결과, 수정 후 시간이 경과되면서 다정자 침입율이 증가되는 것을 볼 수 있었다 그러나 대조구 60.7%에 비해서는 각각 32.5, 36.0, 및 33.3%로 현저히 낮은 것을 볼 수 있었다.(Table Omitted). 또한, 3% sucorse가 첨가된 배양액에서 수정된 수정란의 발달율을 조사한 결과, 배반포 생산율은 처리구 21.8%로 대조구 6.9%에 비해 유의하게 높은 것을 확인 하였다. 따라서, 돼지 난자의 체외수정시 3% sucorse첨가는 체외수정란 생산에서 문제가 되고 있는 다정자 침입율을 저하시키고 배발달율을 향상시킴으로서 수정란의 체외 대량생산 효율성은 물론 수정란 이식시 수태율을 증가시킬 수 있을 것으로 사료된다.

• Reproductive and Developmental Biology
• /
• v.32 no.2
• /
• pp.97-104
• /
• 2008

Plasminogen activators (PAs) are serine protease that cleave plasminogen to form the active protease plasmin. PA/plasmin system playa role in mammalian fertilization and motility and acrosome reaction of sperm. The present study was undertaken to identify PAs in porcine gametes and investigate a possible role of plasminogen in in vitro fertilization in the pig. When boar spermatozoa were preincubated in a fertilization medium (mTBM) for 0, 2, 4 or 6 h, the activity of tPA-PAI ($110{\sim}117\;kDa$), tPA ($62{\sim}70\;kDa$), and uPA ($34{\sim}38\;kDa$) was observed in the sperm incubation medium and sperm sample. PA activities in the sperm incubation medium significantly (p<0.05) increased according to increasing incubation times, while PA activities in sperm significantly (p<0.05) decreased at the same times. In addition, the rate of acrosome reaction in spermatozoa increased by increasing culture times. When oocytes were separated from porcine cumulus-oocytes complexes at 0, 22 or 44 h of maturation culture, no PA activities were observed in cumulus free-oocyte just after aspiration from follicles. However, the activity of tPA-PAI ($108{\sim}113\;kDa$) and tPA ($75{\sim}83\;kDa$) was observed at 22 h of in vitro culture and significantly (p<0.05) increased as the duration of the culture increased. On the other hand, when porcine oocytes were activated by sperm penetration or calcium ionophore, plasminogen significantly (p<0.05) increased ZP dissolution time (sec) in activated oocytes by sperm penetration. These results suggest that supplementation of plasminogen to fertilization medium may playa positive role in the improvement of in vitro fertilization ability in the pig.